M3 not only picked up the reflective properties one would expect from ice, but was able to directly measure the distinctive way its molecules absorb infrared light. This meant that it could differentiate between liquid water and vapour and solid ice.

Temperatures on the Moon can reach a searing 100C in daytime, which doesn’t provide the best conditions for the survival of surface ice.

But because the Moon is tilted on its axis by about 1.54 degrees, there are places at the lunar poles that never see daylight.

Scientists estimate that temperatures in permanently shadowed craters at the Moon’s poles do not rise above -157C (-250F). This would create an environment where deposits of water-ice could remain stable for long periods.

The result supports previous indirect detections of surface ice at the Moon’s south pole. However, those results could potentially be explained by other phenomena – such as unusually reflective lunar soil.

If there’s enough ice sitting at the surface – within the top few millimetres – the water might be accessible as a resource for future human missions to the Moon.

Surface water ice has also been found on other Solar System bodies, such as at the north pole of the planet Mercury and on the dwarf planet Ceres.sci